1. Field of the Invention
The present invention relates to a non-radiative hybrid dielectric line transition which is formed at a junction between different types of non-radiative dielectric lines. In addition, the invention relates to a component, an antenna apparatus, and a wireless apparatus incorporating the same.
2. Description of the Related Art
A dielectric line is used as a transmission line in the millimeter-wave band and the microwave band. Such a dielectric line is formed by disposing a dielectric strip between two approximately parallel conductive plates. Particularly, there is known a first type of non-radiative dielectric line (hereinafter referred to as a xe2x80x9cnormal NRD waveguidexe2x80x9d). In the normal NRD waveguide, a distance between the conductive plates is set to be equal to or less than a half of an electromagnetic-wave propagating wavelength so that the electromagnetic wave propagates only through the dielectric strip.
However, in the normal NRD waveguide, a transmission loss occurs in a bend due to a mode transformation between an LSM01 mode and an LSE01 mode. As a result, a bend having an arbitrary radius of curvature cannot be designed. Thus, a second type of non-radiative dielectric line (hereinafter referred to as a xe2x80x9chyper NRD waveguidexe2x80x9d) has been developed. In the hyper NRD waveguide, a groove is formed in each of the opposing surfaces of the conductive plates, and the dielectric strip is disposed between the grooves to transmit an LSM01 mode as a single mode.
Despite this advantage of the hyper NRD waveguide, if the transmission loss due to the mode transformation in the bend is not considered, the transmission loss of the normal NRD waveguide is smaller than that of the hyper NRD waveguide. The normal NRD waveguide has the further advantage that the transmission loss at a junction of two dielectric strips is less than that in the hyper NRD waveguide.
Therefore, when the normal NRD waveguide is used in a part where the characteristics of the normal NRD waveguide can be exploited and the hyper NRD waveguide is used in a part where the characteristics of the hyper NRD waveguide can be exploited, it is necessary to perform a line transition between the two types of non-radiative dielectric line. The assignee of the present invention describes a structure of a non-radiative hybrid dielectric line transition and an apparatus incorporating the same in Laid-Open Japanese Patent Application Publication No. 11-195910.
However, in a non-radiative hybrid dielectric line transition, as shown in FIG. 3 of the laid-open application, since a second transition is included, extra space is needed both in the line-width direction and line-length direction.
In view of the above-described disadvantage, the present invention provides a non-radiative hybrid dielectric line transition between the aforementioned two different types of non-radiative dielectric line, which is capable of being made smaller than the transition described in the above Japanese Patent Application Publication No. 11-195910.
The present invention further provides a non-radiative dielectric line component, an antenna apparatus, and a wireless apparatus using the non-radiative hybrid dielectric line transition.
According to a first aspect of the present invention, there is provided a non-radiative hybrid dielectric line transition including two conductive planes opposed to each other approximately in parallel, first grooves formed in opposing positions in the two conductive plates, a first non-radiative dielectric line formed by a dielectric strip disposed between the first opposing grooves, a second non-radiative dielectric line formed by a dielectric strip disposed between the two opposing conductive plates, second grooves formed between the first non-radiative dielectric line and the second non-radiative dielectric line, the depths of the second grooves are gradually changed while continuing from the first grooves, and a third non-radiative dielectric line formed by a dielectric strip disposed in the second grooves to form a non-radiative hybrid dielectric line transition connecting the first non-radiative dielectric-line and the second non-radiative dielectric line.
According to a second aspect of the present invention, there is provided a non-radiative hybrid dielectric line transition including two conductive plates forming conductive planes opposed to each other approximately in parallel, first grooves formed in opposing positions in the two conductive plates, a first non-radiative dielectric line formed by a dielectric strip disposed between the first opposing grooves, a second non-radiative dielectric line formed by a dielectric strip disposed between the two opposing conductive plates, second grooves formed between the first non-radiative dielectric line and the second non-radiative dielectric line, the depths of the second grooves being changed in a stepped form while continuing from the first grooves, and a third non-radiative dielectric line formed by a dielectric strip disposed in the second grooves to form a non-radiative hybrid dielectric line transition connecting the first non-radiative dielectric line and the second non-radiative dielectric line.
In this arrangement, in the region of the first non-radiative dielectric line formed by the dielectric strip fitted into the deep grooves, the gaps between the conductive planes of cut-off regions on both sides of the dielectric strip are narrow. In the region of the second non-radiative dielectric line, there are no grooves into which the dielectric strip is fitted, or there are shallow grooves. That is, the gaps between the conductive planes of cut-off regions on both sides of the dielectric strip are wider. As a result, between the region of the first non-radiative dielectric line and the region of the second non-radiative dielectric line, the depths of the grooves, that is, the gaps between the conductive planes of the cut-off regions on both sides of the dielectric strip change, in the region of the third non-radiative dielectric line. In other words, a line transformation between the first and second non-radiative dielectric lines is performed at the third non-radiative dielectric line.
In addition, in the above non-radiative hybrid dielectric line transition, the gaps between the conductive planes of the cut-off regions of the third non-radiative dielectric line may be set to have fixed lengths larger than the gaps of the conductive planes of the cut-off regions of the first non-radiative dielectric line. In addition, the length of the third non-radiative dielectric line in an electromagneticwave propagating direction may be set to be approximately xc2xc of a line wavelength. With this arrangement, the length of the third non-radiative dielectric line serving as the line transition is reduced. Moreover, when a wave reflected at the boundary between the first and third non-radiative dielectric lines is synthesized with a wave reflected at the boundary between the third and second non-radiative dielectric lines, both of the reflected waves are canceled, and a line transformation is performed while reducing reflections and losses. 
According to a third aspect of the present invention, there is provided a non-radiative dielectric line component including the first and second non-radiative dielectric lines described above, with the non-radiative hybrid dielectric line transition disposed at a junction between the first and second non-radiative dielectric lines. For example, in a single module formed by combining a plurality of millimeter-wave circuit components, a junction of lines between the components is formed by the second non-radiative dielectric line, and bends in the components are formed by the first non-radiative dielectric line. In addition, the non-radiative hybrid dielectric line transition is disposed between the first and second non-radiative dielectric lines. As a result, for example, with the use of a hyper NRD waveguide as the first non-radiative dielectric line and a normal NRD waveguide as the second non-radiative dielectric line, the non-radiative dielectric line component of the invention has an overall compact size and reduced transmission loss while exploiting the characteristics of both waveguides.
In addition, in the above non-radiative dielectric line component, two of the second non-radiative dielectric lines may be arranged at a predetermined distance to form a directional coupler, and the first non-radiative dielectric lines may be connected to ends of the two second non-radiative dielectric lines via the third non-radiative dielectric lines. The electric-field energy in the second non-radiative dielectric line distributes more widely than that in the first non-radiative dielectric line. Thus, the above arrangement provides an increased coupling strength between the two second non-radiative dielectric lines forming the directional coupler. Moreover, with the increased coupling strength, since the length of the coupling part between the second non-radiative dielectric lines can be reduced, the overall component can be miniaturized.
According to a fourth aspect of the present invention, there is provided an antenna apparatus including the directional coupler described above. In this antenna apparatus, the directional coupler is divided into a mobile section and a fixed section along an electromagnetic-wave propagating direction at a part where the two second non-radiative dielectric lines forming the directional coupler are coupled to each other. The fixed section includes a dielectric lens, and the mobile section includes a primary radiator. The primary radiator receives a signal transmitted via the directional coupler and radiates the signal via the dielectric lens and sends a signal received from the dielectric lens to the directional coupler.
In this apparatus, the mobile section can be displaced with respect to the fixed section in order to displace the directivity of a beam, while the fixed-section circuit is coupled to the primary radiator via the directional coupler.
According to a fifth aspect of the present invention, there is provided a wireless apparatus including the above non-radiative dielectric line component or the above antenna apparatus to form a millimeter-wave communication apparatus, a millimeter-wave radar, or the like.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings, in which like references denote like elements and parts.